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Abstract

Carbonyl sulfide (OCS) is emitted to the atmosphere through the outgassing of ocean surface waters. OCS is also the primary source of sulfur-containing compounds in the stratosphere and contributes to the formation of the stratospheric sulfate layer, an essential controller of the radiative balance of the atmosphere. During the 2016 Student Airborne Research Program (SARP), 15 whole air samples were collected on the NASA DC-8 aircraft over the Santa Barbara Channel. Five additional surface samples were taken at various locations along the Santa Barbara Channel. The samples were analyzed using gas chromatography in the Rowland-Blake lab at UC Irvine, and compounds associated with ocean emissions including OCS, dimethyl sulfide (DMS), carbon disulfide (CS2), bromoform (CHBr3), and methyl iodide (CH3I) were examined. Excluding OCS, the vertical distribution of marine tracers that were analyzed showed dilution with increasing altitude. For OCS, the surface samples all exhibited elevated concentrations of OCS in comparison to samples taken from the aircraft, with an average of 666 ± 26 pptv, whereas the average concentration of OCS in the aircraft samples was 581 ± 9 pptv. 2016 Surface samples were compared to surface samples from SARP campaigns between 2009-2015 taken near or within the 2016 study region. The 2009-2015 samples exhibited an average OCS concentration of 526 ± 8 pptv. It is evident that the 2016 surface samples measured higher concentrations of OCS than ever recorded during previous SARP campaigns and in comparison to global averages: 525 ± 17 pptv in the Northern hemisphere and 482 ± 13 pptv in the Southern hemisphere (Sturges et al., 2001). OCS emissions should be measured using surface samples if emission estimates from the ocean are to be evaluated since measurements from the aircraft (500 ft) are not sufficiently capturing surface concentrations. Additionally, OCS enhancements seen in 2016 had never before been detected by surface samples, revealing a potential phenomenon at work causing the elevation during this year’s campaign.